1. Field of the Invention
The present invention relates to a plasma display apparatus, and more particularly, to a front filter having a touch screen, and a plasma display apparatus having the same.
2. Description of the Related Art
Plasma display panel (hereinafter referred to as “PDP”) generally displays an image including character or graphic by generating light from fluorescent substance using ultraviolet rays with a wavelength of 147 nm, which is generated during a gas discharge of an inert mixture gas, such as He+Xe, Ne+Xe, He+Ne+Xe or the like. This PDP has easy slimness and large-sized characteristics, and provides a greatly improved picture quality thanks to the recent technology development. Especially, three-electrode alternating current (AC) surface discharge type PDP has advantages of a low voltage operation and a long life since wall charges stored on a surface in the course of discharge protect electrodes from sputtering generated by the discharge.
FIG. 1 is a view illustrating a discharge cell of a conventional three-electrode alternating current (AC) surface discharge type plasma display panel.
Referring to FIG. 1, a discharge cell of the three-electrode AC surface discharge type PDP includes a scan electrode (Y) and a sustain electrode (Z) formed on an upper substrate 10, and an address electrode (X) formed on a lower substrate 18. Each of the scan electrode (Y) and the sustain electrode (z) includes transparent electrodes 12Y and 12Z and metal bus electrodes 13Y and 13Z having line widths narrower than line widths of the transparent electrodes 12Y and 12Z formed at one-sided edge regions of the transparent electrodes 12Y and 12Z.
The transparent electrodes 12Y and 12Z are generally formed of Indium-Tin-Oxide (Hereinafter, referred to as “ITO”) on the upper substrate 10. The metal bus electrodes 13Y and 13Z are generally formed of chrome (Cr) on the transparent electrodes 12Y and 12Z to function to reduce a voltage drop caused by the transparent electrodes 12Y and 12Z having high resistance. An upper dielectric layer 14 and a passivation film 16 are layered on the upper substrate 10 having the scan electrode (Y) and the sustain electrode (z) formed in parallel with each other. The wall charge generated at the time of plasma discharge is stored in the upper dielectric layer 14. The passivation film 16 prevents the upper dielectric layer 14 from being damaged due to the sputtering generating at the time of the plasma discharge and also, enhances an emission efficiency of a secondary electron. Magnesium oxide (Mgo) is generally used as the passivation film 16. A lower dielectric layer 22 and a barrier 24 are formed on the lower substrate 18 having the address electrode (X), and a fluorescent layer 26 is coated on a surface of the lower dielectric layer 22 and the barrier 24. The address electrode (X) is formed in a direction of crossing with the scan electrode (Y) and the sustain electrode (Z). The barrier 24 is formed in parallel with the address electrode (X) to prevent the visible ray and the ultraviolet ray caused by the discharge from being leaked to an adjacent discharge cell. The fluorescent layer 26 is excited by the ultraviolet ray generated due to the plasma discharge to radiate any one visible ray of red, green or blue. The inert mixed gas for the discharge such as He+Xe, Ne+Xe, He+Ne+Xe and the like is injected into a discharge space of the discharge cell provided between the upper/lower substrates 10 and 18 and the barrier 24.
In the PDP, one frame is divided for time-division driving into several sub-fields having different light-emitting times so as to embody a gray level of the image. Each of the sub-fields is divided into a reset period for which an entire screen is initialized, an address period for which a scan line is selected and a specific cell is selected at the selected scan line, and a sustain period for which the gray level is embodied depending on the light-emitting times.
For example, in case that the image is expressed using a 256 gray level as in FIG. 2, a frame period (16.67 ms) corresponding to 1/60 second is divided into eight sub-fields (SF1 to SF8). Also, each of the eight sub-fields (SF1 to SF8) is again divided into a reset period, an address period and a sustain period. Herein, the reset and address periods of each sub-field are identical every sub-field, while as the sustain period is increased in a ratio of 2n (n=0, 1, 2, 3, 4, 5, 6, 7) at each of the sub-fields.
In the above-driven PDP, a front filter for shielding an electronic wave and also preventing an external light from being reflected is installed on a front surface of the upper substrate 10.
FIG. 3 is a schematic section view illustrating a portion of a conventional plasma display apparatus.
Referring to FIG. 3, the conventional plasma display apparatus includes a panel 32 where the upper substrate 10 and the lower substrate 18 are attached to each other with a gap therebetween, a front filter 30 installed at a front surface of the panel 32, a chassis base 36 for supporting the panel 32 and also mounting a printed circuit board thereon, a heat sink plate 34 attached to a front surface of the chassis base 36, a back cover 38 installed on a rear surface of the panel 32, and a front cabinet 45 for electrically connecting the back cover 38 and the front filter 30.
The front cabinet 45 includes a filter support portion 40 for electrically connecting the front filter 30 and the back cover 38, and a support member 42 for fixing and supporting the front filter 30 and the back cover 38. The filter support portion 40 supports the front filter 30 such that a rear surface of the front filter 30 is spaced away from the panel 32. Further, the filter support portion 40 electrically connects the EMI shield film included in the front filter 30 to the back cover 38 grounded to a ground voltage source to discharge an EMI signal from the EMI shield film. Also, the filter support portion 40 prevents the EMI from being laterally emitted.
The printed circuit board mounted on the chassis base 36 supplies a driving signal to electrodes (for example, a scan electrode, a sustain electrode and an address electrode) of the panel 32. For this, the printed circuit board includes various driving portions not shown. The panel 32 displays a certain image in response to the driving signal supplied from the printed circuit board. The heat sink plate 34 dissipates heat generated from the panel 32 and the printed circuit board. The back cover 38 protects the panel 32 from an external impact, and also shields an electromagnetic interference (Hereinafter, referred to as “EMI”) laterally emitted.
The front filter 30 shields the EMI and also, prevents an external light from being reflected. For this, the front filter 30 includes a antireflection coating 50, an optical characteristic film 52, a touch screen 56, and a near infrared ray (Hereinafter, referred to as “NIR”) shield film 58. Herein, an adhesive layer is formed between respective films 50, 52, 56 and 58 of the front filter 30 to adhere respective films 50, 52, 56 and 58 to one another. Generally, a specific substance is added to the adhesive layer to form the optical characteristic film 52. At this time, a structure of the front filter is a little varied depending on a manufacture enterprise.
The antireflection coating 50 prevents an external incident light from being reflected toward an external to improve a contrast of a plasma display panel (PDP). The antireflection coating So is formed on a surface of the front filter 30. Meanwhile, the antireflection coating 50 can be additionally formed on a rear surface of the front filter 30.
The optical characteristic film 52 functions to decrease brightness of red (R) and green (G) of visible ray incident from the panel, while it functions to increase brightness of blue (B) to improve an optical characteristic of the PDP.
The glass 54 prevents the front filter 30 from being damaged by the external impact. That is, the glass 54 supports the front filter 30 to prevent the front filter 30 from being damaged by the external impact.
The EMI shield film 56 shields the EMI to prevent the EMS incident from the panel 32 from being emitted to the external. In the above structure of the EMI shield film 56, a plurality of first electrode lines 61a and a plurality of second electrode lines 61b are crossed with one another for an integral structure. Since the plurality of electrode lines is finely constructed like a black matrix, it does not influence the picture quality.
The NIR shield film 58 shields a NIR (Near Infrared Ray) emitted from the panel 32 to prevent the NIR exceeding a reference value from being emitted toward the external such that a signal transmitting device using IR (Infrared Ray) can normally transmit a signal such as a remote controller and the like. Meanwhile, the EMI shield film 56 and the NIR shield film 58 can be constructed as one layer.
As shown in FIG. 6, the front filter 30 is electrically connected with the back cover 38 through the filter support portion 40. Describing this in detail, the filter support portion 40 is connected to the rear surface of the front filter 30 at one end of the front filter 30. At this time, the filter support portion 40 is electrically connected with at least one of the EMI shield film 56 and the NIR shield film 58. That is, the filter support portion 40 connects the front filter 30 to the back cover 38 to shield the EMI and/or the NIR.
The conventional front filter 30 uses the glass 54 so as to prevent the front filter 30 from being damaged by the external impact. This front filter is called a glass typed front filter. However, if the glass 54 is inserted into the front filter 30, there is a disadvantage in that the front filter 30 is thickened. Further, if the glass 54 is inserted into the front filter 30, there is a drawback in that the front filter 30 is increased in weight and also a manufacture cost.
In order to solve the above drawback, the front filter without the glass has been proposed.
On the other hand, as means for inputting any command on a screen of a display device, a touch screen is widely used.
FIG. 7 is a view illustrating a structure of a conventional touch screen.
The touch screen 70 includes an upper film 72 forming a first transparent conductive layer 74 thereon, and a lower film 76 forming a second transparent conductive layer 78 thereon and being spaced away from the upper film 72.
The upper film 72 and the lower film 76 are united by a sealant 73 coated along an edge portion being a non-touch area and are spaced away from each other as much as a height of the sealant 73. Further, a plurality of spacers (not shown) (for example, dot spacer and the like) is additionally formed on the first transparent conductive layer 74 of the upper film 72 or the second transparent conductive layer 78 of the lower film 76 at a touch area excepting for the non-touch area to separate the upper film 72 from the lower film 76.
A transparent film formed of polyethylene terephthalate (PET) is mainly used as the upper film 72 pressed by a pen or a finger, and a transparent film formed of a material like the upper film 72 is used as the lower film 76. As first and second transparent conductive layers 74 and 78, any one of ITO (Indium-Tin-Oxide), IZO (Indium-Zinc-Oxide) and ITZO (Indium-Tin-Zinc-Oxide) is used.
If the first transparent conductive layer 74 is in contact with the second transparent conductive layer 78 by the upper film 72 pressed by the pen or the finger, a resistance value of the touch screen 70 is varied depending on its contact position. Additionally, since current or voltage is different depending on the varied resistance value, the touch screen 70 output the varied current or voltage as an X-axis coordinate signal through an X electrode bar 75, that is, fist and second X electrode bars 75A and 75B connected to the first transparent conductive layer 74, and outputs as a Y-axis coordinate signal through a Y electrode bar 79, that is, first and second Y electrode bar 79A and 79B connected to the second transparent conductive layer 78. In this case, the touch screen 70 sequentially outputs the X-axis coordinate signal and the Y-axis coordinate signal under control of a touch screen controller (not shown).
As described above, the front filter of the PDP performs an electromagnetic wave shielding function, a color adjustment function, a near infrared absorption function and the like. The touch screen performs a computer function, a home networking function, an automatic power-off function, an internet function and the like.
Accordingly, if the above touch screen is equipped with the plasma display apparatus, the plasma display apparatus does not require an external separate input device, and further can not only appeal to consumer's mentality, but also can enhance a value of a high-class brand.